Borewell - Performance monitoring

Borewell - Performance monitoring

There have been many questions raised in many forums regarding borewell performance, monitoring and maintenance/rehabilitation.

This post shall be dedicated to discussions on these aspects. Here I have discussed the performance aspect of borewells.

Monitoring Boreholes

Processes Affecting Performance
1 Physical Process
Clogging
drilling fluid invasion damage at the time of construction
inter-mixing of aquifer horizons as a result of wash-out and caving during drilling and development
inter-mixing of aquifer and gravel pack material due to poor installation procedure or overaggressive development
migration of fines from the formation into the gravel pack material due to high flows during operation
migration of aquifer material and infilling of the borehole and pumping system

Hydraulic design for a borewell

Administrator

Hydraulic design is very important for sustainable borewell performance. It decides the screen enterance velocity and the vertical velocity inside the borewell. Commonly recommended value for enterance velocity is 0.03 m/s.

It is recommended to take a design value of 0.02 m/s for borewells with problems of incrustation and biofouling. In fissured aquifers the velocity need to be calculated emperically. (compare with existing borewells in same formation; carry out a trial and error to reduce sand ingress)

Reducing enterance velocity / design discharge have many benefits.

Sand ingress is reduced
Erosion of screen slots are reduced
Supply of nutrients are reduced
Loss of kinetic energy is reduced

Re: Borewell Diagnosing and Maintenance/Rehabilitation

Hello, I'd like to seek your guidance on th geological aspects on the design of Borewell on an artificial island. For de watering an area for construction, I'd like to use borewell pumps adjacent to the said site which has a water column height of 9.5 m from the bottom and short of 2. 5 meters from above (the ground level). The area is 4 m in length and 6 meter in breadth. The total volume of water at any point of time is presumably 228 m3 (4x6x9.5). I was thinking of putting 4 borewell pumps of 6 "casing size with 29 m3/hr and suitable head, around the periphery of the site. I'd appreciate your guidance on any precaution to be taken for the job.